Although surgical correction is often the preferred treatment method for strabismus, there can be problems with the outcome. By some accounts, 20-40% of strabismus correction surgeries fail in one way or another and therefore re-operation is required. We suggest that a reason strabismus surgery sometimes fails is that there are adaptive processes that follow the treatment that may work to negate the effects of surgery and revert the eyes to a previous state of misalignment. These adaptive processes might be localized to muscle itself (muscle remodeling) or might involve neural processes (central nervous system remodeling). The goal of this project is to develop a better understanding of the neural adaptive changes that follow strabismus correction surgery which in turn may provide additional insight into reasons for failure or success following treatment. Studies from our laboratory have shown that specially rearing infant monkeys under conditions that disrupted binocular vision reproduced a sensory strabismus syndrome with large horizontal misalignment, A/V patterns, Dissociated Horizontal Deviation (DHD) and Dissociated Vertical Deviation (DVD). Our strategy for this project is first to characterize the neural drive to horizontal extraocular muscles (medial and lateral recti) of the strabismic monkeys by recording from motoneurons in the oculomotor and abducens nuclei. Thereafter, we will treat the strabismus in these animals using similar resection or recession surgery techniques to those used in human patients. Following treatment, we will record neural responses from the same motor nuclei. Comparison of the pre- and post-surgery population neural drive to horizontal extraocular muscles will provide data on how the brain adapts to a muscle strengthening or weakening procedure. In the final aim, we will record from cells in the supraoculomotor area to examine whether the neural adaptation that follows surgical treatments has its origin in vergence circuits. Completion of our studies will be of benefit to the understanding and treatment of developmental forms of strabismus. PUBLIC HEALTH RELEVANCE: Ocular misalignment (strabismus) is a developmental disorder that affects a significant number of children born every year in the United States and around the world. Strabismus correction surgery, a popular treatment method, is often only partially effective. This particular project will examine the neural adaptive response occurring due to surgical treatment of strabismus and determine whether neural changes correlate with the successful or unsuccessful outcome of the treatment. A better understanding of adaptive neural mechanisms that accompany treatments for strabismus may lead to new strategies that will improve outcome of currently used surgical treatment methods.